U.S. patent number 5,187,373 [Application Number 07/756,321] was granted by the patent office on 1993-02-16 for emitter assembly for use in an optical traffic preemption system.
This patent grant is currently assigned to Minnesota Mining and Manufacturing Company. Invention is credited to George A. Gregori.
United States Patent |
5,187,373 |
Gregori |
February 16, 1993 |
Emitter assembly for use in an optical traffic preemption
system
Abstract
An optical signal emitter assembly emits light pulses which are
received by an optical traffic preemption system detector. The
optical signal emitter assembly employs a honeycomb element
positioned in front of a light source which collimates light
emitted by the optical signal emitter assembly. The optical signal
emitter assembly is convertible from a stand-alone unit containing
power supply circuitry, timing circuitry, and a light source in a
single housing, to a unit wherein the light source can be mounted
independently from a housing containing the power supply circuitry
and the timing circuitry.
Inventors: |
Gregori; George A. (New
Brighton, MN) |
Assignee: |
Minnesota Mining and Manufacturing
Company (St. Paul, MN)
|
Family
ID: |
25042976 |
Appl.
No.: |
07/756,321 |
Filed: |
September 6, 1991 |
Current U.S.
Class: |
250/551;
340/906 |
Current CPC
Class: |
G08G
1/087 (20130101) |
Current International
Class: |
G08G
1/087 (20060101); G08G 1/07 (20060101); G02B
027/00 () |
Field of
Search: |
;250/551
;340/471,472,906,907 ;359/354-356,127,129,130,131,641 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
PB91-168039, "Traffic Signal Control Equipment: State of the Art,"
prepared by American Association of State Highway and
Transportation Officials, Washington, D.C., Dec. 1990, pp. 13-15.
.
Opticom.TM. Priority Control System Brochure, "Model 192
Specifications," Safety and Security Systems Division/3M .
"Lightbar Emitter Model 3M9000 Series," Traffic Control Systems
Opticom.TM. Priority Control System Brochure. .
"Z-Crate Visor Model 4102," Indicator Controls Corp. Brochure,
Rancho Dominguez, Calif. 90221..
|
Primary Examiner: Nelms; David C.
Assistant Examiner: Allen; S.
Attorney, Agent or Firm: Griswold; Gary L. Kirn; Walter N.
Barte; William B.
Claims
What is claimed is:
1. An optical signal emitter assembly for remotely controlling
traffic signal lights and adapted to be affixed to an authorized
vehicle, the optical emitter assembly comprising:
a housing;
a light source for converting a supply voltage into a power signal
capable of activating the light source;
timing means coupled to the power supply and the light source, for
controlling the repetition rate and duration of light pulses;
and
collimating means including a honeycomb element having a plurality
of cells, with each cell having an opening that extends form a
front through to a rear of the cell, said element being positioned
in front of the light source, for collimating the light pulses
emitted by the light source thereby resulting in a pulsed light
beam capable of activating a first photodetector channel coupled to
the traffic signal lights to be controlled, while not activating
other photodetector channels proximate to the first photodetector
channel, but coupled to other traffic signal lights which are not
to be controlled.
2. The optical signal emitter assembly of claim 1 and further
comprising a lens positioned in front of the collimating means.
3. The optical signal emitter assembly of claim 2 wherein the lens
is formed from a material that is transparent to visible and
infra-red light.
4. The optical signal emitter assembly of claim 2 wherein the lens
is formed from a material that is opaque to visible light and
transparent to infra-red light.
5. The optical signal emitter assembly of claim 1 wherein a longest
distance across the opening of a cell is approximately 0.25 inches
and a distance between the front and the rear of a cell is
approximately 0.375 inches.
6. The optical signal emitter assembly of claim 5 wherein the
pulsed light beam is generally non-divergent at distances greater
that 500 feet from the optical signal emitter assembly.
7. The optical signal emitter assembly of claim 1 wherein the
honeycomb element is formed from aluminum.
8. The optical signal emitter assembly of claim 1 wherein surfaces
of the honeycomb element are formed from a material which absorbs
visible and infra-red light.
9. The optical signal emitter assembly of claim 1 wherein surfaces
of the honeycomb element are formed form a material which reflects
visible and infra-red light, thereby scattering the light and
resulting in the pulsed light beam having an arc of divergence of
approximately 160 degrees at distances less than 300 feet from the
optical signal emitter assembly.
10. The optical signal emitter assembly of claim 1 and further
comprising a window positioned in front of the collimating means,
the window having the shape of a circle with the top and bottom of
the circle truncated.
11. An optical signal emitter assembly for remotely controlling
traffic signal lights and adapted to be affixed to an authorized
vehicle, the optical emitter assembly comprising:
a housing having first joining means;
a front bezel having second joining means, wherein the second
joining means is adapted to be joined with the first joining
means;
electrical connection means for connecting components in the
housing with components in the front bezel;
a light source positioned in the front bezel, for emitting light
pulses;
a power supply for converting a supply voltage into a power signal
capable of activating the light source;
timing means coupled to the power supply and the light source, for
controlling the repetition rate and duration of light pulses;
and
collimating means including a honeycomb element having a plurality
of cells, with each cell having an opening that extends from a
front through to a rear of the cell, said element being positioned
in the front bezel and in front of the light source, for
collimating the light pulses emitted by the light source thereby
resulting in a pulsed light beam capable of activating a first
photodetector channel coupled to the traffic signal lights to be
controlled, while not activating other photodetector channels
proximate to the first photodetector channel, but coupled to other
traffic signal lights which are not to be controlled.
12. The optical signal emitter assembly of claim 11 wherein the
power supply is positioned in the housing.
13. The optical signal emitter assembly of claim 11 wherein heat
sensitive components of the power supply are positioned in the
front bezel, and a remainder of power supply components are
positioned in the housing.
14. The optical signal emitter assembly of claim 11 wherein the
timing means is positioned in the housing.
15. The optical signal emitter assembly of claim 11 and further
comprising a lens positioned in front of the collimating means.
16. The optical signal emitter assembly of claim 11 and further
comprising mounting means coupled to the housing, for mounting the
housing to a vehicle.
17. The optical signal emitter assembly of claim 11 wherein the
first joining means is joined with the second joining means.
18. The optical signal emitter assembly of claim 11 and further
comprising:
conversion means for allowing the housing to be mounted separately
from the front bezel, the conversion means comprising:
a housing cover having third joining means, wherein the third
joining means is joined with the first joining means; and
a front bezel base having fourth joining means, wherein the second
joining means is joined with the fourth joining means.
19. The optical signal emitter assembly of claim 18 wherein the
bracket spacer has a hole through which the electrical connection
means passes.
20. The optical signal emitter assembly of claim 18 wherein the
front bezel is located on an exterior of a vehicle, the housing is
located at another location of the vehicle and the connection means
is of sufficient length to connect the housing to the front
bezel.
21. The optical signal emitter assembly of c)aim 18 and further
comprising mounting means coupled to the front bezel base, for
mounting the front bezel base to a vehicle.
Description
BACKGROUND OF THE INVENTION
This invention relates to a system that allows authorized vehicles
to remotely control traffic signals, and more specifically, to an
optical signal emitter assembly for use in such a system, wherein
an optical signal emitter assembly attached to an approaching
authorized vehicle transmits a stream of light pulses to a detector
mounted near a traffic intersection causing a preemption request to
be issued to a traffic signal controller.
Traffic signals have long been used to regulate the flow of traffic
at intersections. Generally, traffic signals have relied on timers
or vehicle sensors to determine when to change traffic signal
lights, thereby signaling alternating directions of traffic to
stop, and others to proceed.
Emergency vehicles, such as police cars, fire trucks and
ambulances, generally have the right to cross an intersection
against a traffic signal. Emergency vehicles have typically
depended on horns, sirens and flashing lights to alert other
drivers approaching the intersection that an emergency vehicle
intends to cross the intersection. However, due to hearing
impairment, air conditioning, audio systems and other distractions,
often the driver of a vehicle approaching an intersection will not
be aware of a warning originating from an approaching emergency
vehicle. This can create a dangerous situation when an emergency
vehicle seeks to cross an intersection against a traffic signal and
the driver of another vehicle approaching the intersection is not
aware of the warning being transmitted by the emergency
vehicle.
This problem was first successfully addressed in U.S. Pat. No.
3,550,078 (Long), which is assigned to the same assignee as the
present application. The Long patent discloses an emergency vehicle
with an optical emitter, a plurality of detectors mounted along an
intersection with each detector looking down an approach to the
intersection, a plurality of signal processing circuits located in
the detectors which produce a signal representative of the distance
of the approaching emergency vehicle, and a phase selector which
processes the signal from the processing circuits and can issue a
request to a traffic signal controller to preempt a normal traffic
signal sequence and provide green lights to the approaching
emergency vehicle.
The Long patent discloses that as an emergency vehicle approaches
an intersection, it emits a stream of light pulses at a
predetermined rate, such as 10 pulses per second, and with each
pulse having a duration of several microseconds. A detector
receives the light pulses emitted by the approaching emergency
vehicle. An output of the detector is processed by the phase
selector, which then issues a request to a traffic signal
controller to change to or hold green the traffic signal lights
that control the emergency vehicle's approach to the
intersection.
SUMMARY OF THE INVENTION
This invention provides an optical signal emitter assembly for
remote control use in an optical traffic preemption system. The
invention comprises a housing, a light source for emitting light
pulses, a power supply for converting a supply voltage into a power
signal capable of activating the light source, and timing circuitry
coupled to both the light source and the power supply, for
controlling the repetition rate and duration of the light pulse.
Also, a light collimating honeycomb element is positioned in front
of the light source to collimate the light pulses, resulting in an
optical signal which provides improved control of the traffic
lights to be controlled. The optical emitter of the present
invention is less likely to inadvertently activate an optical
traffic preemption system detector channel proximate to the traffic
signal lights to be controlled, but coupled to traffic signal
lights which are not to be controlled.
The invention is convertible from a stand-alone unit containing
power supply circuitry, timing circuitry, and the light source in a
single housing, to a unit wherein the light source can be mounted
independently from a housing containing the power supply circuitry
and the timing circuitry.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an intersection equipped with a
traffic signal control system in which the optical emitter assembly
of the present invention is mounted on an authorized vehicle
approaching a typical traffic intersection.
FIG. 2 is an exploded view of the optical emitter assembly of FIG.
1.
FIG. 3 is a front view of the optical emitter assembly of FIG.
2.
FIG. 4 is a sectional view taken along line 4--4 of FIG. 3 with
portions thereof shown in full.
FIG. 5 is a diagram showing light beam dispersal patterns for an
optical emitter of the prior art and two embodiments of the present
invention.
FIG. 6 is an exploded view of an alternate embodiment of the
optical emitter assembly of the present invention configured with
an optional kit that allows parts of the assembly to be mounted in
two separate housings.
FIG. 7 is a sectional view of a vehicle body showing an emitter
module mounted through the vehicle body.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is an illustration of a typical intersection 10 with traffic
signal lights 12. A traffic signal controller 14 sequences the
traffic signal lights 12 to allow traffic to proceed alternately
through the intersection. Of particular relevance to the present
invention, the intersection is equipped with an optical traffic
preemption system such as the Opticom.TM. Priority Control System
manufactured by the Minnesota Mining and Manufacturing Company of
Saint Paul, Minn. Such a system includes detector assemblies 16
stationed to detect light pulses from optical emitter assemblies,
one of which (20) is mounted on an authorized emergency vehicle 18,
which is shown approaching the intersection 10 from a westbound
direction. The detector assemblies 16 communicate with a phase
selector 17, which is typically located in the same cabinet as the
traffic controller 14.
The optical emitter assembly 20 transmits light pulses at a
predetermined duration and repetition rate. The detector assembly
16 receives these light pulses and sends an output signal to the
phase selector 17, which processes the signal and issues a request
to the traffic signal controller 14 to preempt a normal traffic
signal sequence. If the optical emitter assembly 20 emits light
pulses at the predetermined repetition rate, with each pulse having
sufficient intensity and fast enough rise time, the phase selector
17 will request the traffic signal controller 14 to cause the
traffic signal lights 12 controlling the north, south and east
bound directions to become or remain red and the traffic signal
lights controlling the westbound direction to become or remain
green.
The present invention makes several improvements over optical
emitters of the prior art. The optical emitter assembly of the
present invention is provided with a honeycomb element which
collimates the emitted light into a generally non-divergent beam. A
non-divergent beam is desirable because it can prevent an
authorized vehicle from activating an optical traffic preemption
system proximate to, but not coupled with the traffic signal lights
to be controlled.
Different embodiments of the honeycomb element can be employed. In
one embodiment, the honeycomb element can have surfaces formed from
a material which reflects light. In this embodiment, the honeycomb
element tends to scatter light at close ranges, while having a
collimating effect at longer ranges. This allows the emitter
assembly to have a wide activation area when it is close to an
optical traffic preemption system detector, yet have a narrow
activation area when it is not close to a detector.
In another embodiment, surfaces of the honeycomb element can be
formed from a material which absorbs light, thereby preventing a
scattering effect. In this embodiment, the honeycomb element only
collimates the emitted light into a generally non-divergent
beam.
The present invention also provides more installation options than
optical emitter assemblies of the prior art. The present invention
is convertible from a stand-alone unit that has the power supply,
timing circuitry and light source in the same housing into a
two-piece unit having the power supply and timing circuitry within
one housing and the light source, reflector, honeycomb element and
lens within another housing. This allows a single design to be
adapted to a wide variety of applications by allowing a user to
purchase a simple kit, thereby reducing manufacturing costs and
providing more flexibility to the user.
FIG. 2 is an exploded view of the optical emitter assembly 20 of
FIG. 1. The optical emitter assembly 20 has a housing 22 and a
front bezel 24. The front bezel 24 can be joined with the housing
22 by placing the front bezel 24 over the housing 22 and inserting
fasteners 27 through the holes 26 to the threaded holes 28. A
gasket 45 seals the interface between the housing 22 and the front
bezel 24.
The housing 22 has a bracket 30, a power supply board 32 and a
timing board 34. The bracket 30 is used to mount the optical
emitter assembly 20 to a vehicle. The power supply board 32
receives a power supply voltage from the vehicle's power supply and
converts the power supply voltage into a power signal, which is
modulated by signals from the timing board 34 to cause a gaseous
discharge lamp 36 to produce a stream of light pulses.
The lamp 36 is positioned within a reflector 38 that directs light
through a honeycomb element 40. The reflector 38 has an opening
above and below the lamp 36, providing ventilation to the area
surrounding the lamp 36, thereby preventing the lamp 36 from
overheating and damaging surrounding components.
The honeycomb element 40, which is constructed of aluminum,
collimates light into a beam that is generally non-divergent at
distances over 500 feet. In one embodiment, the aluminum surfaces
of the honeycomb element 40 are exposed and reflect light so that
at closer ranges, such as under 300 feet, the element 40 tends to
scatter light into a beam having an arc of divergence of
approximately 160 degrees.
In another embodiment, the honeycomb element 40 is coated with a
visible and infra-red light absorbing material, such as black
paint. In this embodiment, the element 40 only collimates light
into a beam which is generally non-divergent. It does not scatter
light at closer ranges.
After light emitted by the lamp 36 passes through the honeycomb
element 40, it passes through a lens 42. In one embodiment, the
lens 42 is constructed of a material that is transparent to
infra-red and visible light. The preferred material for such a lens
is a clear polycarbonate plastic, such as Lexan.TM. 123, which is a
product of the General Electric Company.
In another embodiment, the lens 42 is constructed of a material
which is opaque to visible light, but is transparent to infra-red
light. The preferred material for such a lens is an acrylic plastic
formed with a visible light blocking dye, such as Material No. V811
with Color No. 58189, manufactured by Rohm-Hass. In this
embodiment, an observer watching an operating optical emitter
assembly 20, will not be able to perceive that the emitter is in
operation. An optical emitter assembly having a lens 42 constructed
of a material opaque to visible light and transparent to infra-red
light will have a range that is approximately 25 to 50 percent less
than the range of an optical emitter assembly having a lens 42
constructed of material which is transparent to visible and
infra-red light.
Window 46 has the shape of a circle with the top and bottom of the
circle truncated. In other embodiments, window 46 may assume other
shapes, such as an oval or a rectangle. A gasket 44 is positioned
between the lens 42 and front bezel 24 to seal and weather-proof
the assembly. The gasket 44 has an opening similar in shape to that
of the window 46 of the front bezel 24.
FIG. 3 is a front view of the optical emitter assembly 20 and shows
that the honeycomb element 40 is constructed of a plurality of
cells 48. Each cell has an opening which extends from the front
through to the rear of the cell and has a generally hexagonal shape
with two sides equal to a first length and four sides equal to a
second length. The first length is approximately 0.125 inches and
the second length is approximately 0.188 inches. The longest
distance across the opening of a cell is approximately 0.25 inches.
These dimensions give the cells a somewhat horizontally squashed
appearance. The preferred honeycomb material is manufactured by
Hexcel Corporation and is available under part number
ACG-1/4-4.8P.
FIG. 4 is a sectional view taken along line 4--4 of FIG. 3 with
portions thereof shown in full. FIG. 4 shows the orientation of the
honeycomb element 40 with respect to the lamp 36. When the lamp 36
emits light pulses, light coming directly from the lamp 36 and
light reflected by the reflector 38 passes through the honeycomb
element 40. The honeycomb element 40 is approximately 0.375 inches
thick and produces a light beam which is generally non-divergent at
ranges greater than 500 feet.
In the embodiment where the honeycomb element 40 has reflective
surfaces, the interior surfaces of the cells 48 will scatter light
at closer distances, resulting in a light beam having an arc of
divergence of 160 degrees at ranges less than 300 feet. In the
embodiment where the honeycomb element 40 has surfaces which absorb
visible and infra-red light, the light which passes through the
honeycomb element 40 is only collimated by the cells 48 and is not
scattered.
FIG. 4 also shows a pulse transformer 37, which produces a high
voltage output signal and is part of the emitter power supply. The
pulse transformer 37 is sensitive to heat and its high voltage
output signal is difficult to transmit without causing electrical
breakdown. For this reason, the pulse transformer 37 has been
mounted to the front bezel 24. This location is cooler than a
location on power supply board 32 and allows the high voltage
output signal to be connected directly to lamp 36, thereby reducing
the possibility of electrical breakdown.
FIG. 5 is a diagram showing typical light beam dispersal patterns
for an optical emitter of the prior art and two embodiments of the
present invention. An optical traffic preemption detector within an
emitter's dispersal pattern will be activated if the emitter is
transmitting a valid optical signal.
The range of an optical traffic preemption system is primarily
dependent on the power of the optical emitter and the sensitivity
of the detector. The dispersal patterns shown in FIG. 5 are based
on emitter/detector combinations that have an effective range of
approximately 2000 feet; a typical range for an optical traffic
preemption system. The primary purpose of FIG. 5 is to show the
dispersal patterns of the present invention and prior art emitters,
not the ranges of emitter/detector combinations.
The line 39 represents a dispersal pattern for a typical optical
emitter of the prior art. At a range of 1250 feet, the arc of
divergence of the beam is greater than 60 degrees, which results in
beam that is greater than 1500 feet wide at this range. Such a
dispersal pattern is large enough to activate optical traffic
preemption detector channels which are proximate to the traffic
signals to be controlled, but are coupled to other traffic signal
lights which are not to be controlled.
The lines 41, 43 and 47 represent the dispersal patterns of two of
the embodiments of the present invention. The line 41 represents
the embodiment where the honeycomb element 40 has reflective
surfaces and scatters light, while the line 43 represents the
embodiment where the honeycomb element 40 is coated with a material
which absorbs visible and infra-red light. The point 45 is where
the optical characteristics of the two embodiments converge. The
two embodiments have similar optical characteristics in the region
represented by the line 47.
At 1250 feet, both embodiments of the present invention have an arc
of divergence of approximately 40 degrees, which results in a beam
that is less than 850 feet wide at this range. Compared to optical
emitters of the prior art, this narrow beam is much less likely to
inadvertently activate an optical traffic preemption system
detector channel which is proximate to the traffic signal lights to
be controlled, but coupled to traffic signal lights which are not
to be controlled.
FIG. 6 is an exploded view of an alternative embodiment in which
the optical emitter assembly 20 is configured with an optional kit
that allows the power supply board 32 and the timing board 34 to be
mounted independently from the lamp 36, the reflector 38, the
honeycomb element 40 and the front bezel 24. This optional kit is
comprised of a housing cover 52, a cable 54 and a front bezel base
56, a bracket spacer 67, a mounting bracket 64 and some additional
fasteners.
To convert the stand-alone optical emitter assembly 20 of FIG. 2
into the two-part emitter assembly of FIG. 6, which has emitter
module 58 and supply module 68, the reflector 38, the lamp 36, the
honeycomb element 40, the lens 42, the gasket 44 and the front
bezel 24 are removed from the housing 22. In place of the front
bezel 24, the housing cover 52 is placed over the housing 22. The
housing cover 52 is similar to the front bezel 24 and is joined
with the housing 22 by inserting fasteners through the holes 60 to
the threaded holes 28. A cable 54, which is secured to bracket
spacer 67, couples the circuitry on the power supply board 32 and
the timing board 34 to the lamp 36, which is housed in the front
bezel base 56. The front bezel base 56 can be joined with the front
bezel 24 by inserting fasteners through the holes 26 to the
threaded holes 62. The emitter module 58 can be mounted on a
vehicle by using the bracket 64.
Emitter module 58 can also be mounted to an opening of a vehicle
body, as shown in FIG. 7 where emitter module 58 is mounted to a
body 70 of a vehicle. In this mounting configuration, knock-out
holes 66 (also shown in FIG. 6) are opened so that fasteners 72 can
attach the emitter assembly 58 to body 70. The supply module 68 can
be mounted in a convenient location and connected to the emitter
module 58 with cable 54.
Although the present invention has been described with reference to
preferred embodiments, workers skilled in the art will recognize
that changes may be made in form and detail without departing from
the spirit and scope of the invention.
* * * * *